Solvent compositions are in widespread use throughout the world and in a wide variety of industrial applications. Certain fluorocarbons have been preferred components in solvent cleaning systems for many years. Trichlorotrifluoroethane has been one of the most widely used fluorocarbon solvents in recent years because it is generally effective as a solvent for many greases, oils, waxes and the like, and has therefore found widespread use for cleaning electric motors, compressors, heavy metal parts, delicate precision metal parts, printed circuit boards, gyroscopes, guidance systems, aerospace and missile hardware, aluminum parts, and the like. Furthermore, trichlorotrifluoroethane is advantageous because it is nontoxic and nonflammable. Trichlorotrifluoroethane has two isomers: 1,1,2-trichloro-1,2,2-trifluoroethane (known in the art as CFC-113) and 1,1,1-trichloro-2,2,2-trifluoroethane (known in the art as CFC-113a).
Concern has increased in recent years about potential damage to the earth's ozone layer, and certain chlorine-based compounds have been identified as particularly problematic in this regard. CFC-113 is chemically stable and therefore has a relatively long life in the stratosphere, and since the use CFC-113 as a solvent will frequently result in its release into the environment, it will frequently reach the stratosphere. In the stratosphere, CFC-113 gives rise to photolysis under the influence of sun light to generate chlorine radicals. The thus generated chlorine radicals combine with ozone, resulting in ozone depletion. Accordingly, the use of organic chlorine-based compounds such as CFCs has been severely restricted in many countries of the world by governmental regulation. Because CFC-113 has a high ozone depletion potential (ODP), a need has risen to replace it, and other compounds which exhibit similar environmentally detrimental properties.
Applicants have thus come to appreciate a continuing need for low ODP and low global warming potential (GWP) solvent compositions that are potentially useful in numerous applications, including degreasing applications, precision cleaning and electronics cleaning applications, dry cleaning applications, solvent etching applications, as a solvent in aerosols or other sprayable compositions, as carrier solvents for depositing lubricants and release agents and other solvent or surface treatment applications.
In many applications it is also highly desirable for solvent compositions to be relatively stable, that is, to be relatively resistant to possible chemical changes during storage and use. Applicants have come to recognize that CFC-113 is deficient in this regard because it tends to hydrolyze and form HCl. Furthermore, this problem is worsened because metal, which is typically present during any solvent cleaning operations, acts as a catalyst and causes the hydrolysis of CFC-113 to increase dramatically.
The compositions of the present invention are thus part of a continued search for the next generation of low global warming potential materials. Such materials must have low environmental impact, as measured by ultra-low global warming potential and zero ozone depletion potential.
The preferred compositions of the present invention are environmentally acceptable and do not to contribute to the depletion of the earth's stratospheric ozone layer. The compounds and compositions of the present invention have no substantial ozone depletion potential, preferably an ODP of not greater than about 0.5 and even more preferably an ODP of not greater than about 0.25, most preferably an ODP of not greater than about 0.1; a global warming potential (GWP) of not greater than about 150, and even more preferably, a GWP of not greater than about 50.
As used herein, ODP is defined in the “Scientific Assessment of Ozone Depletion, 2002, ” a report of the World Meteorological association, incorporated here by reference.
As used herein, GWP is defined relative to that of carbon dioxide and over a 100 year time horizon, and defined in the same reference as for the ODP mentioned above.
As used herein, the term “nonflammable” refers to compounds or compositions which do not exhibit a flashpoint as measured by one of the standard flash point methods, for example ASTM-1310-86 “Flash point of liquids by tag Open-cup apparatus.” Unfortunately, many HFC's which might otherwise be desirable for use in solvent compositions are flammable. For example, the fluoroalkane pentafluorobutane (HFC-365) is flammable and therefore not viable for use in many applications.